Someone at the village must've told them about the American hunter up here.
2 seconds sound clip from the The Treasure of the Sierra Madre movie soundboard.
You can hear this line at 01:04:26.183 in the Blu-ray version of the movie.
Quote context
[...]
- Can't make out what they are. Must be soldiers.
- You're wrong, brother. This means all our funerals.
- If that's what I think it is, may the lord be with us.
- They're not soldiers. They're bandits, and they're not after gold, but after guns and ammunition.
- Someone at the village must've told them about the American hunter up here.
- They don't look like soldiers to me, either.
- That's what they are, all right... bandits.
[...]